HSDIO PXI-6541Acquisition at which clock edge?

[jcao]

Hi,
 
I am using PXI-6541 for generation and acquisition. I am using "Start Trig: Pat. Match" to configure "NIHSDIO Configure Trigger.vi" function, and I am using "On Board Clock" for "NIHSDIO Configure Sample Clock" for both acquisition and generation process.
 
My question is: In which clock edge is the HSDIO sampling while doing acquisition, falling, rising, or 50% duration, etc? I am doing my scan test and realize the acquisition results is one sample difference from the expected result. I would like to change the acquisition sampling method (say, from falling edge to rising edge, or vice versa), but don't know how to do that.
 
Anybody could help me on this?
 
Thank you very much!
Jing

[NI-Bongo]

Hi Jing, I think this <a href="http://digital.ni.com/public.nsf/allkb/A70921E707DF94C0862571D800097A7C?OpenDocument" target="_blank">KnowledgeBase article</a> will give you the solution you are looking for: Missing the First Sample with NI-HSDIO Deviceshttp://digital.ni.com/public.nsf/allkb/A70921E707DF94C0862571D800097A7C?OpenDocumentLet me know if this helps!

[jcao]

Hi John,
Thank you for your help.
I understand that when I use "Start Trigger: Digital Edge" at function "NIHSDIO Configure Trigger", I can select falling edge or&nbsp;rising edge of the clock.
My question is: now I am using "Start Trigger: Pattern Match" as the trigger starting point for acquisition, so the HSDIO card will start acquisition at which edge of the clock after the pattern is matched?
Thank you,
Jing

[NI-Bongo]

Hi again Jing, I was able to change the property suggested in the KnowledgeBase article without the software throwing an error, even with a Pattern Match Start Trigger.&nbsp; Did you try this?&nbsp; If so, what was the result?&nbsp; I didn't have a test signal handy to check for the correct behavior, but I was able to change the property.If this doesn't work, another workaround would be to use a reference trigger to acquire a pretrigger sample.&nbsp; Would this be an adequate workaround for your application?

[DJ L.]

Hey Jing,
&nbsp;
To answer your following question:
Q: "Now I am using "Start Trigger: Pattern Match" as the trigger starting point for acquisition, so the HSDIO card will start acquisition at which edge of the clock after the pattern is matched?"
&nbsp;
A: The default edge, if you do not specify one, is the Rising Edge of the clock. But I think the real answer&nbsp;that you are looking for is the following: You can&nbsp;and will probably want to&nbsp;use the niHSDIO Configure Data Position.VI to set which edge of the clock that you want to acquire on after the pattern is matched. There is a Position input that gives you the following options:

- Sample Clock Rising Edge

- Sample Clock Falling Edge

- Delay from Rising Edge of Sample Clock

If you choose Delay from Rising Edge of Sample Clock, you will need to specify the delay using the delay parameter of the <a href="mk:@MSITStore:C:\Program%20Files\National%20Instruments\LabVIEW%208.5\help\hsdio.chm::/hsdio_config_delay.html" target="_blank">Configure Data Position Delay</a>&nbsp;VI.
I hope this answers your question. Please let us know if you need any further help or clarification on this issue. Thanks, and have a great day.
Regards,DJ L.

[jcao]

Hi DJ and John,
Thanks a lot for your help. I used the VI function DJ suggested and it works.
Thanks again!
Jing